Abstract: Disclosed is a force applying device for orthodontic treatment being elastically expandable and configured to generate a restoring force as an orthodontic force for an orthodontic treatment when compressed. The force applying device comprises a first element and a second element capable of moving relative to each other along a first axis. The force applying device for orthodontic treatment is compressed when the first and second elements move towards each other along the first axis. A first arm extends laterally from a first end of the first element away from the second element. A first connecting part of a first connector is fitted over the first arm. A second connecting part of the first connector is to be fitted over a button fixed on a first jaw to connect the first element to the first jaw. Both the first and the second connecting parts are toroidal in shape.

Abstract: A protection circuit of a communication interface includes: a first-level protection circuit, a second-level protection circuit and a third-level protection circuit that are sequentially connected, wherein the first-level protection circuit comprises a current discharge circuit comprising a first connection end, a second connection end and a third connection end, wherein the first connection end is connected with a first signal line of an RS-485 port, the second connection end is connected with a second signal line of the RS-485 port, and the third connection end is connected to the protection ground; the second-level protection circuit comprises a first current limiting resistor, a second current limiting resistor and a bidirectional transient suppression diode; and the third-level protection circuit comprises a voltage discharge circuit.

Abstract: A protection circuit of a communication interface includes: a first-level protection circuit, a second-level protection circuit and a third-level protection circuit that are sequentially connected, wherein the first-level protection circuit comprises a current discharge circuit comprising a first connection end, a second connection end and a third connection end, wherein the first connection end is connected with a first signal line of an RS-485 port, the second connection end is connected with a second signal line of the RS-485 port, and the third connection end is connected to the protection ground; the second-level protection circuit comprises a first current limiting resistor, a second current limiting resistor and a bidirectional transient suppression diode; and the third-level protection circuit comprises a voltage discharge circuit.